Quasi-yagi antenna based on double-sided parallel-strip line

Abstract

Recently, planar quasi-yagi antenna become renewed interest because of its suitability for a wide range of applications like wireless communication system. For the conventional design, the additional balun is required in the feed network of the antenna, which occupies large PCB area and only provides exact 180 degree phase difference in a narrow frequency range. In this project, quasi-yagi antenna designed using double-sided parallel-strip line (DSPSL) is proposed to solve the problem. Based on the DSPSL feed line, the out-of-phase feature becomes frequency independent and the design of antenna becomes much simpler. Furthermore, an active component named push-pull oscillator would also be proposed in the project in order to provide a RF power source to the quasi-yagi antenna. The push-pull oscillator consists of two identical sub-oscillators which share a common DSPSL and a common ground. The anti-phase signals generated by the two sub-oscillators directly feed to the antenna for radiation, and the in-phase second harmonics are cancelled out at the DSPSL feed line of the antenna.